Digi NS9215 - Manual (Page 122)

W O R K I N G W I T H T H E C P U
Fault checking sequence
122 Hardware Reference NS9215
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F a u l t c h e c k i n g s e q u e n c e
The sequence the MMU uses to check for access faults is different for sections and
pages. The next figure shows the sequence for both types of access.
AP S R Privileged permissions User permissions
0 0 0 0 No access No access
0 0 1 0 Read only Read only
0 0 0 1 Read only Read only
0 0 1 1 UNPREDICTABLE UNPREDICTABLE
0 1 x x Read/write No access
1 0 x x Read/write Read only
1 1 x x Read/write Read/write